This was just in a test project and the abbreviations were empty - I just had the short names (which were set to Mat, Mar), and the References were set to use the short name. When I added the abbreviations, it started working as expected. So I thought I had found a bug ("if the abbreviation is empty, the Extra Material doesn't work", or something like that...). But then I removed the abbreviations again... and it still worked! So I'm not sure exactly what happened, but it looks like if you have the abbreviations and short names filled in, the Extra Material should probably work as expected. Thanks for your input.